Variable drag ogive



Dec. 23, 1969 ALTITUDE w. J. MERTENS 3,485,460

VARIABLE DRAG OGIVE Filed Feb. 19, 1968 VARIABLE DRAG OGIVE RANGE CHANGE AT CONSTANT QE ll SECON D TR AJ ECTORY QE OGIIVE c BOTH CASES I00 200 300 460 560 e00 700 860 960 1000 I100 I200 RANGE (Yds.)

WILLIAM J. MERTENS ATTORN EY.

United States Patent 3,485,460 VARIABLE DRAG OGIVE William J. Martens, Richmond, Ind., assignor to Avco Corporation, Richmond, Ind., a corporation of Delaware Filed Feb. 19, 1968, Ser. No. 706,593 Int. Cl. F42b 15/10 U.S. Cl. 244-3.1 2 Claims ABSTRACT OF THE DISCLOSURE The invention is a variable drag rocket-type projectile provided with means to change the ogive so that the range of the projectile can be controlled in the field by a simple manual manipulation.

THE INVENTION Military projectiles are usually designed with ogives which offer minimum aerodynamic drag to allow maximum performance in flight. For certain purposes, however, particularly in the case of relatively short range rockets, it is desirable to have available a projectile for enfiladed targets, which are difficultly reached by longer range rocket rounds by reason of their flat, rifle-like trajectory. Accordingly, a mortar-type trajectory is desirable for such a target in order to neutralize the existence of an enfilade.

In the case of a rocket powered flare it is likewise desirable to vary the shape of the trajectory without requiring a change in the fixed impulse of the rocket in order to change the range of the trajectory without adversely affecting the time of flight.

An object of the invention is to provide a rocket-type projectile construction in which one or more ogives can be selected and easily fitted in the field to permit the launching of a round with either a smooth rounded ogive with consistent transition from ogive to bourrelet, with minimum drag and maximum range or alternatively, a flat ogive with relatively sharp edges with maximum drag and minimum range, or still further alternatively, with some intermediate ogive.

A further object is to provide for different ranges for a fixed impulse projectile such as a rocket round without major changes in launcher quadrant or elevation.

A further object is to provide a selection of ogives which can be made quickly and easily in the practical environment in which the round must be used.

A still further object is to provide more flexibility in adjusting the range of muzzle-fired projectiles.

Other objects and advantages of the invention will more clearly appear when reference is had to the accompanying drawings, in which:

FIG. 1 is a fragmentary cross-sectional view of a rocket type projectile constructed of two detachable sections each having a characteristic aerodynamic drag factor;

FIG. 2 illustrates the maximum and minimum trajactory to be achieved with two of the ogives shown in FIG. 1.

In FIG. 1 illustrative rocket casing D is provided with a flat circular plastic ogive member A permanently attached to the aluminum or steel housing using an adhesive or snap-on arrangement. The fiat ogive is provided with a central axial depressed portion threaded to receive shank or projection 11 comprising a secant type ogive B. Preferably the threads are treated with antifriction material such as tough, heat resistant plastic in order to require relatively high torque for removal. The threads should be cut right handed to permit the ogive to tighten when fired from a launcher having a right hand twist barrel.

Ogive C is a spherical or tangential. ogive and for accommodation with the structure shown is provided with external threads 12 fitting into internal threads 13 cut into an enlarged portion 14 of shank 11, the threads being likewise right hand threads. The threads 12, 13 are desirably treated so that ogive C can be more easily removed. Suitable apertures (not shown) may be provided for the insertion of appropriate spanner wrenches to permit assembly and disassembly, but otherwise no special tooling is required for the structure shown.

In FIG. 2 I have shown trajectories for ogives A and C computed from a rocket round designed for a range of 800 to 1,000 yards and fired at approximately a 45 angle from the horizontal. It will be observed that ogive A has a slightly higher trajectory but much shorter range, permitting the round to drop nearly vertically at an 800 yard target, while ogive C permits a much longer trajectory permitting the round to fall on a target at an acute angle. The fixed impulse in each case of this illustration allows 11 seconds trajectory time, thereby utilizing the motive force of the round to a maximum extent. The maximum burnout velocity of the round at the shorter range is reduced without reducing the maximum potential of the built-in motive forces of the rocket. This is contrary to the usual objective in exterior ballistic prob lems where it is desired to achieve maximum performance under all conditions.

While I have shown screw-threaded means for attachment of the various ogives, it is to be understood that other means such as snap-in or break-off devices can be used without departing from the principle herein disclosed.

Having described my invention, I claim:

1. A projectile adapted to be fired at a given elevation and to reach a predetermined range and incorporating means adapted to be installed in the field for providing a predetermined range and incrementally increasing the range in a predictable manner, without change in launcher elevation or driving power for the projectile, said projectile comprising:

a casing and the means for providing a predetermined range and incrementally extending the range of the projectiles comprising a plurality of ogives, the ogives being related to each other in a series of decreasingly blunt facial contours so that the securing of each additional ogive in front of the preceding ogive provides an increment in range and decrement in aerodynamic drag,

said plurality of ogives comprising a first flat ogive secured to said casing to provide maximum aerodynamic drag and minimum range, the flat ogive being formed centrally with an axially extending interiorly threaded well,

each additional ogive being of mushroom configuration and formed with a rearwardly extending exteriorly threaded shank and a central interiorly threaded well adapted to receive the shank of a succeeding ogive, and

each adjacent well and shank constituting complementary formations for detacha'bly securing each additional ogive to the preceding ogive, so as to achieve some incremental increase in range.

2. A projectile adapted to be fired at a given elevation and to reach a predetermined range, and incorporating means adapted to be installed in the field for providing a predetermined range and incrementally increasing the range in a predictable manner, without change in launcher elevation or driving power for the projectile, said projectile comprising:

a casing and the means for providing a predetermined range and incrementally extending the range of the projectile comprising a plurality of ogives, the ogives -being related to each other in a series of decreasingly blunt facial contours so that the securing of each additional ogive in front of the preceding ogive provides an increment in range and a decrement in aerodynamic drag,

said plurality of ogives comprising a first fiat ogive secured to said casing to provide maximum aerodynamic drag and minimum range, the flat ogive being formed centrally with a socket,

each additional ogive being of mushroom configuration and formed with a rearwardly extending plug and a central socket adapted to receive the plug of a succeeding ogive, and

each adjacent plug and socket being complementary formations for detachably securing each additional ogive to the preceding ogive, so as to achieve some incremental increase in range.

References Cited UNITED STATES PATENTS VERLIN R. PENDEGRASS, Primary Examiner 

